Patent GB-308007-A (GB)
Title: Improvements in concrete and like mixers
IPC: B28C7/02
Filed: 1928-01-09
Abstract: 308,007. Robb, J. F. Jan. 9, 1928. Rotary mixers; feeding; discharging. - A concrete &c. mixer, fitted with a timing-device for controlling the period of the mixing operation, is provided with automatic means for operating the discharge mechanism synchronously with the charging-devices whereby the drum is charged without waste of time, hand gear being provided for temporarily throwing out of operation the automatic means if the charging or discharging has to be suspended. In the form shown, the mixing plant is supported on an endless track for transport and comprises a rotary drum D, Fig. 1, which is discharged by means of a pivoted shoot 8 and charged by a pivoted skip G hoisted into charging position by a winch 18; a predetermined quantity of water is - fed to the drum withthe dry materials by means of a three-way cock 21 in communication with the drum, a main 33, and a tank 31 respectively. The timing-device 6, Fig. 5, is adapted, at the end of the mixing period, to rock the shaft 6<x>, whereby the link 6b is moved downwards. The link 6b is connected to a three-armed lever pivoted at 6<d>; one of the arms 6<c> is connected by a pin-and-slot to a link 19 the other end of which is connected by a second pin-and-slot with a lever 64, Fig. 2, which is engaged by a projection 17<1> on the loading skip when the latter is raised, the timing-device being thus reset. Mounted on the link 19 is a stop 19<a> which engages a stop on a link 24 connected at one end with the three-way cock 21 and at the other to a link 22 pivoted to a lever 20 engaged by the projection 17<1> when the loading-skip is in its lower position. The cock is thus alternately turned. to connect the main 33 and tank 31, and the tank and drum, so that a definite quantity of water is supplied to each batch. The other arm 6<f>, Fig. 5, of the threearmed lever is connected to a link 88, the lower end of which operates a cam 91 which engages a lever 92. One end of the lever 92 engages a clutch 81 on a constantly-rotating shaft 80 and drives a worm 82 thereon in engagement with a worm wheel 83; simultaneously a nose 94 on the other end of the lever 92 is released from a recess 95 in the edge of a disc 96 driven frictionally from the worm wheel 83. The disc 96 is mounted on a sleeve 84 which carries a pair of cams 84<a> adapted to engage a lever 12 and a single cam 84f which is adapted to engage a lever 6<a> The lever 12 is connected to a link 51, the lower pivoted end 51<a>, Fig. 3, of which is formed as a cam riding between stops 63. A latch 52 is carried by the part 57a and engages an arm 50 on a lever 48, the upper end 54 of which engages a pin 47 on a disc 44 and moves it into one of a series of holes in a constantly driven worm wheel 46. The disc 44 carrying a crank arm 11<a> is thus rotated half a turn until a cam 55 re-engages the pin 47 to effect disengagement with the worm wheel. The crank arm 11<a> operates a link 11, Fig. 2, which tilts the shoot 8, Fig. 1, to and from its discharging positions. The lever 6<a>, Fig. 2, is connected to a link 30 which, through connecting links 15, 16 and a spring 37, engages the lower end of a clutch lever 14 operating the winch 18 to raise the leading skip. The raising- gear for the skip is arranged to hold the skip at its upward limit a few seconds and then lower it under brake control. For this purpose the winch drum is fitted with a rotor 66, Fig. 4 fitted with centrifugal weighted levers 67 connected by toggle-links 68 with the ends of a pair of brake shoes 69. The latter act in the interior of a drum 70 fitted with ratchet teeth co-operating with a pawl 72, and a band 74 controlled by a lever 75 actuated through a dash pot by the link 30. The operations are timed so that the skip is raised so as to be in charging position as soon as the discharge of the drum is completed. The manual control for suspending the charging and discharging operations comprises a lever 14a, Fig. 2, controlling the clutch 17. By holding the clutch out of operation charging is suspended, the spring 37 and slot connection 39 permitting the idle movement of the link 30, while, if the lever is moved to the right a linkage 27<a> 27, 26, Fig. 2 moves a stop 28 into position to prevent the operation of the lever 12 controlling the discharge shoot.